Hand signals. I like the hand signal given by the ground crew to the pilots when clearance is given to pressurise the hydraulic systems in the 737. They bang on the side of the fuselage under the copilots window, prompting him to open the window (if its not raining that is) and peer out. The bloke below then places two fingers into his two eyes (very carefully of course). This means it is clear to "pressyoureyes". Pressurize.....Gitit?